Whole-Body Control with Motion/Force Transmissibility for Parallel-Legged Robot

TL;DR

This paper introduces an MFT-enhanced whole-body control scheme for parallel-legged robots, improving their dynamic performance by incorporating motion/force transmissibility indices as constraints, validated through simulations and experiments.

Contribution

It develops an offline method to incorporate MFT indices into WBC as a polyhedral constraint, enabling high-speed, robust control of parallel-legged robots.

Findings

Achieved 1kHz control rate with the proposed method.

Enhanced robot performance in simulations and experiments.

Validated robustness and effectiveness of the approach.

Abstract

For achieving kinematically suitable configurations and highly dynamic task execution, an efficient way is to consider robot performance indices in the whole-body control (WBC) of robots. However, current WBC methods have not considered the intrinsic features of parallel robots, especially motion/force transmissibility (MFT). This paper proposes an MFT-enhanced WBC scheme for parallel-legged robots. Introducing the performance indices of MFT into a WBC is challenging due to the nonlinear relationship between MFT indices and the robot configuration. To overcome this challenge, we establish the MFT preferable space of the robot offline and formulate it as a polyhedron in the joint space at the acceleration level. Then, the WBC employs the polyhedron as a soft constraint. As a result, the robot possesses high-speed and high-acceleration capabilities by satisfying this constraint. The offline preprocessing relieves the online computation burden and helps the WBC achieve a 1kHz servo rate. Finally, we validate the performance and robustness of the proposed method via simulations and experiments on a parallel-legged bipedal robot.